Pension And Other Postretirement Benefits (Information For Pension Plans With A Benefit Obligation In Excess Of Plan Assets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Benefit obligation	$ 763,600	$ 679,261
Plan assets	495,082	426,384
Benefit obligation in excess of plan assets	268,518	252,877
Indianapolis Power And Light Company [Member]
Benefit obligation	763,600	679,261
Plan assets	495,082	426,384
Benefit obligation in excess of plan assets	$ 268,518	$ 252,877